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.Dd July 9, 2025
.Dt LIBUSB 3
.Os
.Sh NAME
.Nm libusb
.Nd "USB access library"
.Sh LIBRARY
USB access library
.Pq libusb, -lusb
.Sh SYNOPSIS
.In libusb.h
.Sh DESCRIPTION
The
.Nm
library contains interfaces for directly managing a usb device.
The current implementation supports v1.0 of the libusb API.
.Sh LIBRARY INITIALISATION AND DEINITIALISATION
.Ft "const struct libusb_version *"
.Fn libusb_get_version "void"
This function returns version information about LibUSB.
.Pp
.Ft int
.Fn libusb_init "libusb_context **ctx"
Call this function before any other libusb v1.0 API function, to
initialise a valid libusb v1.0 context.
If the
.Fa ctx
argument is non-NULL, a pointer to the libusb context is stored at
the given location.
This function returns 0 upon success or LIBUSB_ERROR on failure.
.Pp
.Ft int
.Fn libusb_init_context "libusb_context **ctx" "const struct libusb_init_option []" "int num_options"
Call this function before any other libusb v1.0 API function, to
initialise a valid libusb v1.0 context.
If the
.Fa ctx
argument is non-NULL, a pointer to the libusb context is stored at
the given location.
Additional options, like the USB debug level, may be given using the
second and third argument.
If no options are needed, simply use libusb_init().
This function returns 0 upon success or a LIBUSB_ERROR value on failure.
.Pp
.Ft void
.Fn libusb_exit "libusb_context *ctx"
Deinitialise libusb.
Must be called at the end of the application.
Other libusb routines may not be called after this function.
.Pp
.Ft int
.Fn libusb_has_capability "uint32_t capability"
This function checks the runtime capabilities of
.Nm .
This function will return non-zero if the given
.Fa capability
is supported, 0 if it is not supported.
The valid values for
.Fa capability
are:
.Bl -tag -width LIBUSB_CAP -offset indent
.It Va LIBUSB_CAP_HAS_CAPABILITY
.Nm
supports
.Fn libusb_has_capability .
.It Va LIBUSB_CAP_HAS_HOTPLUG
.Nm
supports hotplug notifications.
.It Va LIBUSB_CAP_HAS_HID_ACCESS
.Nm
can access HID devices without requiring user intervention.
.It Va LIBUSB_CAP_SUPPORTS_DETACH_KERNEL_DRIVER
.Nm
supports detaching of the default USB driver with
.Fn libusb_detach_kernel_driver .
.El
.Pp
.Ft const char *
.Fn libusb_strerror "int code"
Get the ASCII representation of the error given by the
.Fa code
argument.
This function does not return NULL.
.Pp
.Ft int
.Fn libusb_setlocale "const char *locale"
Set locale for the error message when using
.Fn libusb_strerror
to
.Ft locale .
Note other
.Nm
implementations only support the first two bytes, that means
.Ql en-US
is equivalent to
.Ql en-CA .
.Pp
.Ft const char *
.Fn libusb_error_name "int code"
Get the ASCII representation of the error enum given by the
.Fa code
argument.
This function does not return NULL.
.Pp
.Ft void
.Fn libusb_set_debug "libusb_context *ctx" "int level"
Set the debug level to
.Fa level .
.Sh DEVICE HANDLING AND ENUMERATION
.Ft ssize_t
.Fn libusb_get_device_list "libusb_context *ctx" "libusb_device ***list"
Populate
.Fa list
with the list of usb devices available, adding a reference to each
device in the list.
All the list entries created by this
function must have their reference counter
decremented when you are done with them,
and the list itself must be freed.
This
function returns the number of devices in the list or a LIBUSB_ERROR code.
.Pp
.Ft void
.Fn libusb_free_device_list "libusb_device **list" "int unref_devices"
Free the list of devices discovered by libusb_get_device_list.
If
.Fa unref_device
is set to 1 all devices in the list have their reference
counter decremented once.
.Pp
.Ft uint8_t
.Fn libusb_get_bus_number "libusb_device *dev"
Returns the number of the bus contained by the device
.Fa dev .
.Pp
.Ft uint8_t
.Fn libusb_get_port_number "libusb_device *dev"
Returns the port number which the device given by
.Fa dev
is attached to.
.Pp
.Ft int
.Fn libusb_get_port_numbers "libusb_device *dev" "uint8_t *buf" "uint8_t bufsize"
Stores, in the buffer
.Fa buf
of size
.Fa bufsize ,
the list of all port numbers from root for the device
.Fa dev .
.Pp
.Ft int
.Fn libusb_get_port_path "libusb_context *ctx" "libusb_device *dev" "uint8_t *buf" "uint8_t bufsize"
Deprecated function equivalent to libusb_get_port_numbers.
.Pp
.Ft uint8_t
.Fn libusb_get_device_address "libusb_device *dev"
Returns the device_address contained by the device
.Fa dev .
.Pp
.Ft enum libusb_speed
.Fn libusb_get_device_speed "libusb_device *dev"
Returns the wire speed at which the device is connected.
See the LIBUSB_SPEED_XXX enums for more information.
LIBUSB_SPEED_UNKNOWN is returned in case of unknown wire speed.
.Pp
.Ft int
.Fn libusb_get_max_packet_size "libusb_device *dev" "unsigned char endpoint"
Returns the wMaxPacketSize value on success, LIBUSB_ERROR_NOT_FOUND if the
endpoint does not exist and LIBUSB_ERROR_OTHERS on other failure.
.Pp
.Ft int
.Fn libusb_get_max_iso_packet_size "libusb_device *dev" "unsigned char endpoint"
Returns the packet size multiplied by the packet multiplier on success,
LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist and
LIBUSB_ERROR_OTHERS on other failure.
.Pp
.Ft libusb_device *
.Fn libusb_ref_device "libusb_device *dev"
Increment the reference counter of the device
.Fa dev .
.Pp
.Ft void
.Fn libusb_unref_device "libusb_device *dev"
Decrement the reference counter of the device
.Fa dev .
.Pp
.Ft int
.Fn libusb_wrap_sys_device "libusb_context *ctx" "intptr_t sys_dev" "libusb_device_handle **dev_handle"
This function creates a libusb handler from a previously opened fd
.Fa sys_dev .
This function is provided for compatibility and is currently unimplemented.
It always returns
.Dv LIBUSB_ERROR_NOT_SUPPORTED .
.Pp
.Ft int
.Fn libusb_open "libusb_device *dev" "libusb_device_handle **devh"
Open a device and obtain a device_handle.
Returns 0 on success,
LIBUSB_ERROR_NO_MEM on memory allocation problems, LIBUSB_ERROR_ACCESS
on permissions problems, LIBUSB_ERROR_NO_DEVICE if the device has been
disconnected and a LIBUSB_ERROR code on other errors.
.Pp
.Ft libusb_device_handle *
.Fn libusb_open_device_with_vid_pid "libusb_context *ctx" "uint16_t vid" "uint16_t pid"
A convenience function to open a device by vendor and product IDs
.Fa vid
and
.Fa pid .
Returns NULL on error.
.Pp
.Ft void
.Fn libusb_close "libusb_device_handle *devh"
Close a device handle.
.Pp
.Ft libusb_device *
.Fn libusb_get_device "libusb_device_handle *devh"
Get the device contained by devh.
Returns NULL on error.
.Pp
.Ft libusb_device *
.Fn libusb_get_parent "libusb_device *dev"
Get dev's parent device.
Returns NULL if the device has no parent (i.e. is a root device).
.Pp
.Ft int
.Fn libusb_get_configuration "libusb_device_handle *devh" "int *config"
Returns the value of the current configuration.
Returns 0
on success, LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
and a LIBUSB_ERROR code on error.
.Pp
.Ft int
.Fn libusb_set_configuration "libusb_device_handle *devh" "int config"
Set the active configuration to
.Fa config
for the device contained by
.Fa devh .
This function returns 0 on success, LIBUSB_ERROR_NOT_FOUND if the requested
configuration does not exist, LIBUSB_ERROR_BUSY if the interfaces are currently
claimed, LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and a
LIBUSB_ERROR code on failure.
.Pp
.Ft int
.Fn libusb_claim_interface "libusb_device_handle *devh" "int interface_number"
Claim an interface in a given libusb_handle
.Fa devh .
This is a non-blocking function.
It returns 0 on success, LIBUSB_ERROR_NOT_FOUND
if the requested interface does not exist, LIBUSB_ERROR_BUSY if a program or
driver has claimed the interface, LIBUSB_ERROR_NO_DEVICE if the device has
been disconnected and a LIBUSB_ERROR code on failure.
.Pp
.Ft int
.Fn libusb_release_interface "libusb_device_handle *devh" "int interface_number"
This function releases an interface.
All the claimed interfaces on a device must be released
before closing the device.
Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if the
interface was not claimed, LIBUSB_ERROR_NO_DEVICE if the device has been
disconnected and LIBUSB_ERROR on failure.
.Pp
.Ft int
.Fn libusb_set_interface_alt_setting "libusb_device_handle *dev" "int interface_number" "int alternate_setting"
Activate an alternate setting for an interface.
Returns 0 on success,
LIBUSB_ERROR_NOT_FOUND if the interface was not claimed or the requested
setting does not exist, LIBUSB_ERROR_NO_DEVICE if the device has been
disconnected and a LIBUSB_ERROR code on failure.
.Pp
.Ft int
.Fn libusb_clear_halt "libusb_device_handle *devh" "unsigned char endpoint"
Clear an halt/stall for a endpoint.
Returns 0 on success, LIBUSB_ERROR_NOT_FOUND
if the endpoint does not exist, LIBUSB_ERROR_NO_DEVICE if the device has been
disconnected and a LIBUSB_ERROR code on failure.
.Pp
.Ft int
.Fn libusb_reset_device "libusb_device_handle *devh"
Perform an USB port reset for an usb device.
Returns 0 on success,
LIBUSB_ERROR_NOT_FOUND if re-enumeration is required or if the device has
been disconnected and a LIBUSB_ERROR code on failure.
.Pp
.Ft int
.Fn libusb_check_connected "libusb_device_handle *devh"
Test if the USB device is still connected.
Returns 0 on success,
LIBUSB_ERROR_NO_DEVICE if it has been disconnected and a LIBUSB_ERROR
code on failure.
.Pp
.Ft int
.Fn libusb_kernel_driver_active "libusb_device_handle *devh" "int interface"
Determine if a driver is active on a interface.
Returns 0 if no kernel driver is active
and 1 if a kernel driver is active, LIBUSB_ERROR_NO_DEVICE
if the device has been disconnected and a LIBUSB_ERROR code on failure.
.Pp
.Ft int
.Fn libusb_get_driver "libusb_device_handle *devh" "int interface" "char *name" "int namelen"
or
.Ft int
.Fn libusb_get_driver_np "libusb_device_handle *devh" "int interface" "char *name" "int namelen"
Copy the name of the driver attached to the given
.Fa device
and
.Fa interface
into the buffer
.Fa name
of length
.Fa namelen .
Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if no kernel driver is attached
to the given interface and LIBUSB_ERROR_INVALID_PARAM if the interface does
not exist.
This function is non-portable.
The buffer pointed to by
.Fa name
is only zero terminated on success.
.Pp
.Ft int
.Fn libusb_detach_kernel_driver "libusb_device_handle *devh" "int interface"
or
.Ft int
.Fn libusb_detach_kernel_driver_np "libusb_device_handle *devh" "int interface"
Detach a kernel driver from an interface.
This is needed to claim an interface already claimed by a kernel driver.
Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if no kernel driver was active,
LIBUSB_ERROR_INVALID_PARAM if the interface does not exist,
LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
and a LIBUSB_ERROR code on failure.
This function is non-portable.
.Pp
.Ft int
.Fn libusb_attach_kernel_driver "libusb_device_handle *devh" "int interface"
Re-attach an interface kernel driver that was previously detached.
Returns 0 on success,
LIBUSB_ERROR_INVALID_PARAM if the interface does not exist,
LIBUSB_ERROR_NO_DEVICE
if the device has been disconnected, LIBUSB_ERROR_BUSY if the driver cannot be
attached because the interface is claimed by a program or driver and a
LIBUSB_ERROR code on failure.
.Pp
.Ft int
.Fn libusb_set_auto_detach_kernel_driver "libusb_device_handle *devh" "int enable"
This function enables automatic kernel interface driver detach when an
interface is claimed.
When the interface is restored the kernel driver is allowed to be re-attached.
If the
.Fa enable
argument is non-zero the feature is enabled.
Else disabled.
Returns 0 on success and a LIBUSB_ERROR code on
failure.
.Pp
.Ft unsigned char *
.Fn libusb_dev_mem_alloc "libusb_device_handle *devh"
This function attempts to allocate a DMA memory block from the given
.Fa devh
so that we can enjoy the zero-copy transfer from kernel.
This function is provided for compatibility and is currently unimplemented and always returns NULL.
.Pp
.Ft int
.Fn libusb_dev_mem_free "libusb_device_handle *devh" "unsigned char *buffer" "size_t size"
This function frees the DMA memory in
.Fa devh
from the given
.Fa buffer
with
.Fa size .
This function is unimplemented and always returns LIBUSB_ERROR_NOT_SUPPORTED.
.Sh USB DESCRIPTORS
.Ft int
.Fn libusb_get_device_descriptor "libusb_device *dev" "libusb_device_descriptor *desc"
Get the USB device descriptor for the device
.Fa dev .
This is a non-blocking function.
Returns 0 on success and a LIBUSB_ERROR code on
failure.
.Pp
.Ft int
.Fn libusb_get_active_config_descriptor "libusb_device *dev" "struct libusb_config_descriptor **config"
Get the USB configuration descriptor for the active configuration.
Returns 0 on
success, LIBUSB_ERROR_NOT_FOUND if the device is in
an unconfigured state
and a LIBUSB_ERROR code on error.
.Pp
.Ft int
.Fn libusb_get_config_descriptor "libusb_device *dev" "uint8_t config_index" "libusb_config_descriptor **config"
Get a USB configuration descriptor based on its index
.Fa idx .
Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if the configuration does not exist
and a LIBUSB_ERROR code on error.
.Pp
.Ft int
.Fn libusb_get_config_descriptor_by_value "libusb_device *dev" "uint8 bConfigurationValue" "libusb_config_descriptor **config"
Get a USB configuration descriptor with a specific bConfigurationValue.
This is
a non-blocking function which does not send a request through the device.
Returns 0
on success, LIBUSB_ERROR_NOT_FOUND if the configuration
does not exist and a
LIBUSB_ERROR code on failure.
.Pp
.Ft void
.Fn libusb_free_config_descriptor "libusb_config_descriptor *config"
Free a configuration descriptor.
.Pp
.Ft int
.Fn libusb_get_string_descriptor "libusb_device_handle *devh" "uint8_t desc_idx" "uint16_t langid" "unsigned char *data" "int length"
Retrieve a string descriptor in raw format.
Returns the number of bytes actually transferred on success
or a negative LIBUSB_ERROR code on failure.
.Pp
.Ft int
.Fn libusb_get_string_descriptor_ascii "libusb_device_handle *devh" "uint8_t desc_idx" "unsigned char *data" "int length"
Retrieve a string descriptor in C style ASCII.
Returns the positive number of bytes in the resulting ASCII string
on success and a LIBUSB_ERROR code on failure.
.Pp
.Ft int
.Fn libusb_parse_ss_endpoint_comp "const void *buf" "int len" "libusb_ss_endpoint_companion_descriptor **ep_comp"
This function parses the USB 3.0 endpoint companion descriptor in host endian format pointed to by
.Fa buf
and having a length of
.Fa len .
Typically these arguments are the extra and extra_length fields of the
endpoint descriptor.
On success the pointer to resulting descriptor is stored at the location given by
.Fa ep_comp .
Returns zero on success and a LIBUSB_ERROR code on failure.
On success the parsed USB 3.0 endpoint companion descriptor must be
freed using the libusb_free_ss_endpoint_comp function.
.Pp
.Ft void
.Fn libusb_free_ss_endpoint_comp "libusb_ss_endpoint_companion_descriptor *ep_comp"
This function is NULL safe and frees a parsed USB 3.0 endpoint companion descriptor given by
.Fa ep_comp .
.Pp
.Ft int
.Fn libusb_get_ss_endpoint_companion_descriptor "struct libusb_context *ctx" "const struct libusb_endpoint_descriptor *endpoint" "struct libusb_ss_endpoint_companion_descriptor **ep_comp"
This function finds and parses the USB 3.0 endpoint companion descriptor given by
.Fa endpoint .
Returns zero on success and a LIBUSB_ERROR code on failure.
On success the parsed USB 3.0 endpoint companion descriptor must be
freed using the libusb_free_ss_endpoint_companion_descriptor function.
.Pp
.Ft void
.Fn libusb_free_ss_endpoint_companion_descriptor "struct libusb_ss_endpoint_companion_descriptor *ep_comp"
This function is NULL safe and frees a parsed USB 3.0 endpoint companion descriptor given by
.Fa ep_comp .
.Pp
.Ft int
.Fn libusb_get_bos_descriptor "libusb_device_handle *handle" "struct libusb_bos_descriptor **bos"
This function queries the USB device given by
.Fa handle
and stores a pointer to a parsed BOS descriptor into
.Fa bos .
Returns zero on success and a LIBUSB_ERROR code on failure.
On success the parsed BOS descriptor must be
freed using the libusb_free_bos_descriptor function.
.Pp
.Ft int
.Fn libusb_parse_bos_descriptor "const void *buf" "int len" "libusb_bos_descriptor **bos"
This function parses a Binary Object Store, BOS, descriptor into host endian format pointed to by
.Fa buf
and having a length of
.Fa len .
On success the pointer to resulting descriptor is stored at the location given by
.Fa bos .
Returns zero on success and a LIBUSB_ERROR code on failure.
On success the parsed BOS descriptor must be freed using the
libusb_free_bos_descriptor function.
.Pp
.Ft void
.Fn libusb_free_bos_descriptor "libusb_bos_descriptor *bos"
This function is NULL safe and frees a parsed BOS descriptor given by
.Fa bos .
.Pp
.Ft int
.Fn libusb_get_usb_2_0_extension_descriptor "struct libusb_context *ctx" "struct libusb_bos_dev_capability_descriptor *dev_cap" "struct libusb_usb_2_0_extension_descriptor **usb_2_0_extension"
This function parses the USB 2.0 extension descriptor from the descriptor given by
.Fa dev_cap
and stores a pointer to the parsed descriptor into
.Fa usb_2_0_extension .
Returns zero on success and a LIBUSB_ERROR code on failure.
On success the parsed USB 2.0 extension descriptor must be freed using the
libusb_free_usb_2_0_extension_descriptor function.
.Pp
.Ft void
.Fn libusb_free_usb_2_0_extension_descriptor "struct libusb_usb_2_0_extension_descriptor *usb_2_0_extension"
This function is NULL safe and frees a parsed USB 2.0 extension descriptor given by
.Fa usb_2_0_extension .
.Pp
.Ft int
.Fn libusb_get_ss_usb_device_capability_descriptor "struct libusb_context *ctx" "struct libusb_bos_dev_capability_descriptor *dev_cap" "struct libusb_ss_usb_device_capability_descriptor **ss_usb_device_capability"
This function parses the SuperSpeed device capability descriptor from the descriptor given by
.Fa dev_cap
and stores a pointer to the parsed descriptor into
.Fa ss_usb_device_capability .
Returns zero on success and a LIBUSB_ERROR code on failure.
On success the parsed SuperSpeed device capability descriptor must be freed using the
libusb_free_ss_usb_device_capability_descriptor function.
.Pp
.Ft void
.Fn libusb_free_ss_usb_device_capability_descriptor "struct libusb_ss_usb_device_capability_descriptor *ss_usb_device_capability"
This function is NULL safe and frees a parsed SuperSpeed device capability descriptor given by
.Fa ss_usb_device_capability .
.Pp
.Ft int
.Fn libusb_get_container_id_descriptor "struct libusb_context *ctx" "struct libusb_bos_dev_capability_descriptor *dev_cap" "struct libusb_container_id_descriptor **container_id"
This function parses the container ID descriptor from the descriptor given by
.Fa dev_cap
and stores a pointer to the parsed descriptor into
.Fa container_id .
Returns zero on success and a LIBUSB_ERROR code on failure.
On success the parsed container ID descriptor must be freed using the
libusb_free_container_id_descriptor function.
.Pp
.Ft void
.Fn libusb_free_container_id_descriptor "struct libusb_container_id_descriptor *container_id"
This function is NULL safe and frees a parsed container ID descriptor given by
.Fa container_id .
.Pp
.Ft int
.Fn libusb_get_platform_descriptor "struct libusb_context *ctx" "struct libusb_bos_dev_capability_descriptor *dev_cap" "struct libusb_platform_descriptor **platform_descriptor"
This function parses the platform descriptor from the descriptor given by
.Fa dev_cap
and stores a pointer to the parsed descriptor into
.Fa platform_descriptor .
Returns zero on success and a LIBUSB_ERROR code on failure.
On success the parsed platform descriptor must be freed using the
libusb_free_platform_descriptor function.
.Pp
.Ft void
.Fn libusb_free_platform_descriptor "struct libusb_platform_descriptor *platform_descriptor"
This function is NULL safe and frees a parsed platform descriptor given by
.Fa platform_descriptor .
.Sh USB ASYNCHRONOUS I/O
.Ft struct libusb_transfer *
.Fn libusb_alloc_transfer "int iso_packets"
Allocate a transfer with the number of isochronous packet descriptors
specified by
.Fa iso_packets .
Returns NULL on error.
.Pp
.Ft void
.Fn libusb_free_transfer "struct libusb_transfer *tr"
Free a transfer.
.Pp
.Ft int
.Fn libusb_submit_transfer "struct libusb_transfer *tr"
This function will submit a transfer and returns immediately.
Returns 0 on success, LIBUSB_ERROR_NO_DEVICE if
the device has been disconnected and a
LIBUSB_ERROR code on other failure.
.Pp
.Ft int
.Fn libusb_cancel_transfer "struct libusb_transfer *tr"
This function asynchronously cancels a transfer.
Returns 0 on success and a LIBUSB_ERROR code on failure.
.Sh USB SYNCHRONOUS I/O
.Ft int
.Fn libusb_control_transfer "libusb_device_handle *devh" "uint8_t bmRequestType" "uint8_t bRequest" "uint16_t wValue" "uint16_t wIndex" "unsigned char *data" "uint16_t wLength" "unsigned int timeout"
Perform a USB control transfer.
Returns the actual number of bytes
transferred on success, in the range from and including zero up to and
including
.Fa wLength .
On error a LIBUSB_ERROR code is returned, for example
LIBUSB_ERROR_TIMEOUT if the transfer timed out, LIBUSB_ERROR_PIPE if the
control request was not supported, LIBUSB_ERROR_NO_DEVICE if the
device has been disconnected and another LIBUSB_ERROR code on other failures.
The LIBUSB_ERROR codes are all negative.
.Pp
.Ft int
.Fn libusb_bulk_transfer "struct libusb_device_handle *devh" "unsigned char endpoint" "unsigned char *data" "int length" "int *transferred" "unsigned int timeout"
Perform an USB bulk transfer.
A timeout value of zero means no timeout.
The timeout value is given in milliseconds.
Returns 0 on success, LIBUSB_ERROR_TIMEOUT
if the transfer timed out, LIBUSB_ERROR_PIPE if the control request was not
supported, LIBUSB_ERROR_OVERFLOW if the device offered more data,
LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and
a LIBUSB_ERROR code on other failure.
.Pp
.Ft int
.Fn libusb_interrupt_transfer "struct libusb_device_handle *devh" "unsigned char endpoint" "unsigned char *data" "int length" "int *transferred" "unsigned int timeout"
Perform an USB Interrupt transfer.
A timeout value of zero means no timeout.
The timeout value is given in milliseconds.
Returns 0 on success, LIBUSB_ERROR_TIMEOUT
if the transfer timed out, LIBUSB_ERROR_PIPE if the control request was not
supported, LIBUSB_ERROR_OVERFLOW if the device offered more data,
LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and
a LIBUSB_ERROR code on other failure.
.Sh USB STREAMS SUPPORT
.Ft int
.Fn libusb_alloc_streams "libusb_device_handle *dev" "uint32_t num_streams" "unsigned char *endpoints" "int num_endpoints"
This function verifies that the given number of streams using the
given number of endpoints is allowed and allocates the resources
needed to use so-called USB streams.
Currently only a single stream per endpoint is supported to simplify
the internals of LibUSB.
This function returns 0 on success or a LIBUSB_ERROR code on failure.
.Pp
.Ft int
.Fn libusb_free_streams "libusb_device_handle *dev" "unsigned char *endpoints" "int num_endpoints"
This function release resources needed for streams usage.
Returns 0 on success or a LIBUSB_ERROR code on failure.
.Pp
.Ft void
.Fn libusb_transfer_set_stream_id "struct libusb_transfer *transfer" "uint32_t stream_id"
This function sets the stream ID for the given USB transfer.
.Pp
.Ft uint32_t
.Fn libusb_transfer_get_stream_id "struct libusb_transfer *transfer"
This function returns the stream ID for the given USB transfer.
If no stream ID is used a value of zero is returned.
.Sh USB EVENTS
.Ft int
.Fn libusb_try_lock_events "libusb_context *ctx"
Try to acquire the event handling lock.
Returns 0 if the lock was obtained and 1 if not.
.Pp
.Ft void
.Fn libusb_lock_events "libusb_context *ctx"
Acquire the event handling lock.
This function is blocking.
.Pp
.Ft void
.Fn libusb_unlock_events "libusb_context *ctx"
Release the event handling lock.
This will wake up any thread blocked
on
.Fn libusb_wait_for_event .
.Pp
.Ft int
.Fn libusb_event_handling_ok "libusb_context *ctx"
Determine if it still OK for this thread to be doing event handling.
Returns 1
if event handling can start or continue.
Returns 0 if this thread must give up
the events lock.
.Pp
.Ft int
.Fn libusb_event_handler_active "libusb_context *ctx"
Determine if an active thread is handling events.
Returns 1 if there is a thread handling events and 0 if there
are no threads currently handling events.
.Pp
.Ft void
.Fn libusb_interrupt_event_handler "libusb_context *ctx"
Causes the
.Fn libusb_handle_events
familiy of functions to return to the caller one time.
The
.Fn libusb_handle_events
functions may be called again after calling this function.
.Pp
.Ft void
.Fn libusb_lock_event_waiters "libusb_context *ctx"
Acquire the event_waiters lock.
This lock is designed to be obtained in the
situation where you want to be aware when events are completed, but some other
thread is event handling so calling
.Fn libusb_handle_events
is not allowed.
.Pp
.Ft void
.Fn libusb_unlock_event_waiters "libusb_context *ctx"
Release the event_waiters lock.
.Pp
.Ft int
.Fn libusb_wait_for_event "libusb_context *ctx" "struct timeval *tv"
Wait for another thread to signal completion of an event.
Must be called
with the event waiters lock held, see
.Fn libusb_lock_event_waiters .
This will
block until the timeout expires or a transfer completes or a thread releases
the event handling lock through
.Fn libusb_unlock_events .
Returns 0 after a
transfer completes or another thread stops event handling, and 1 if the
timeout expired.
.Pp
.Ft int
.Fn libusb_handle_events_timeout_completed "libusb_context *ctx" "struct timeval *tv" "int *completed"
Handle any pending events by checking if timeouts have expired and by
checking the set of file descriptors for activity.
If the
.Fa completed
argument is not equal to NULL, this function will
loop until a transfer completion callback sets the variable pointed to
by the
.Fa completed
argument to non-zero.
If the
.Fa tv
argument is not equal to NULL, this function will return
LIBUSB_ERROR_TIMEOUT after the given timeout.
Returns 0 on success, or a LIBUSB_ERROR code on failure or timeout.
.Pp
.Ft int
.Fn libusb_handle_events_completed "libusb_context *ctx" "int *completed"
Handle any pending events by checking the set of file descriptors for activity.
If the
.Fa completed
argument is not equal to NULL, this function will
loop until a transfer completion callback sets the variable pointed to
by the
.Fa completed
argument to non-zero.
Returns 0 on success, or a LIBUSB_ERROR code on failure.
.Pp
.Ft int
.Fn libusb_handle_events_timeout "libusb_context *ctx" "struct timeval *tv"
Handle any pending events by checking if timeouts have expired and by
checking the set of file descriptors for activity.
Returns 0 on success, or a
LIBUSB_ERROR code on failure or timeout.
.Pp
.Ft int
.Fn libusb_handle_events "libusb_context *ctx"
Handle any pending events in blocking mode with a sensible timeout.
Returns 0
on success and a LIBUSB_ERROR code on failure.
.Pp
.Ft int
.Fn libusb_handle_events_locked "libusb_context *ctx" "struct timeval *tv"
Handle any pending events by polling file descriptors, without checking if
another thread is already doing so.
Must be called with the event lock held.
.Pp
.Ft int
.Fn libusb_pollfds_handle_timeouts "libusb_context *ctx"
This function determines whether applications maintaining libusb events using
.Fn libusb_get_pollfds
are responsible for handling timeout events themselves.
Returns 1 if libusb handles the timeout internally, 0 if the application
needs to set a dedicated timer to handle it.
.Pp
.Ft int
.Fn libusb_get_next_timeout "libusb_context *ctx" "struct timeval *tv"
Determine the next internal timeout that libusb needs to handle.
Returns 0
if there are no pending timeouts, 1 if a timeout was returned, or a LIBUSB_ERROR
code on failure or timeout.
.Pp
.Ft void
.Fn libusb_set_pollfd_notifiers "libusb_context *ctx" "libusb_pollfd_added_cb added_cb" "libusb_pollfd_removed_cb remove_cb" "void *user_data"
Register notification functions for file descriptor additions/removals.
These functions will be invoked for every new or removed file descriptor
that libusb uses as an event source.
.Pp
.Ft const struct libusb_pollfd **
.Fn libusb_get_pollfds "libusb_context *ctx"
Retrieve a list of file descriptors that should be polled by your main loop as
libusb event sources.
Returns a NULL-terminated list on success or NULL on failure.
.Pp
.Ft int
.Fn libusb_hotplug_register_callback "libusb_context *ctx" "libusb_hotplug_event events" "libusb_hotplug_flag flags" "int vendor_id" "int product_id" "int dev_class" "libusb_hotplug_callback_fn cb_fn" "void *user_data" "libusb_hotplug_callback_handle *handle"
This function registers a hotplug filter.
The
.Fa events
argument select which events makes the hotplug filter trigger.
Available event values are LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED and LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT.
One or more events must be specified.
The
.Fa vendor_id ,
.Fa product_id
and
.Fa dev_class
arguments can be set to LIBUSB_HOTPLUG_MATCH_ANY to match any value in the USB device descriptor.
Else the specified value is used for matching.
If the
.Fa flags
argument is set to LIBUSB_HOTPLUG_ENUMERATE, all currently attached and matching USB devices will be passed to the hotplug filter, given by the
.Fa cb_fn
argument.
Else the
.Fa flags
argument should be set to LIBUSB_HOTPLUG_NO_FLAGS.
This function returns 0 upon success or a LIBUSB_ERROR code on failure.
.Pp
.Ft int
.Fn libusb_hotplug_callback_fn "libusb_context *ctx" "libusb_device *device" "libusb_hotplug_event event" "void *user_data"
The hotplug filter function.
If this function returns non-zero, the filter is removed.
Else the filter is kept and can receive more events.
The
.Fa user_data
argument is the same as given when the filter was registered.
The
.Fa event
argument can be either of LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED or LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT.
.Pp
.Ft void
.Fn libusb_hotplug_deregister_callback "libusb_context *ctx" "libusb_hotplug_callback_handle handle"
This function unregisters a hotplug filter.
.Pp
.Ft void
.Fn libusb_free_pollfds "const struct libusb_pollfd **pollfds"
This function releases the memory storage in
.Fa pollfds ,
and is safe to call when the argument is NULL.
.Pp void *
.Fn libusb_hotplug_get_user_data "struct libusb_context *ctx" "libusb_hotplug_callback_handle callback_handle"
This function returns the user data from the opaque
.Fa callback_handle ,
or returns NULL if no matching handle is found.
.Sh LIBUSB VERSION 0.1 COMPATIBILITY
The library is also compliant with LibUSB version 0.1.12.
.Pp
.Fn usb_open
.Fn usb_close
.Fn usb_get_string
.Fn usb_get_string_simple
.Fn usb_get_descriptor_by_endpoint
.Fn usb_get_descriptor
.Fn usb_parse_descriptor
.Fn usb_parse_configuration
.Fn usb_destroy_configuration
.Fn usb_fetch_and_parse_descriptors
.Fn usb_bulk_write
.Fn usb_bulk_read
.Fn usb_interrupt_write
.Fn usb_interrupt_read
.Fn usb_control_msg
.Fn usb_set_configuration
.Fn usb_claim_interface
.Fn usb_release_interface
.Fn usb_set_altinterface
.Fn usb_resetep
.Fn usb_clear_halt
.Fn usb_reset
.Fn usb_strerror
.Fn usb_init
.Fn usb_set_debug
.Fn usb_find_busses
.Fn usb_find_devices
.Fn usb_device
.Fn usb_get_busses
.Fn usb_check_connected
.Fn usb_get_driver_np
.Fn usb_detach_kernel_driver_np
.Sh SEE ALSO
.Xr libusb20 3 ,
.Xr usb 4 ,
.Xr usbconfig 8 ,
.Xr usbdump 8
.Pp
.Lk https://libusb.info/
.Sh HISTORY
.Nm
support first appeared in
.Fx 8.0 .
